How Does Air Get into the Braking System?

Are you worried about the braking performance of your car? The pedal may appear to travel further than normal when you're bringing the vehicle to a halt, or it may feel a little spongy underfoot. While this is something that you should certainly investigate as soon as possible, what could be causing this strange behaviour?

The Passage of Time

In an ideal world, the brakes fitted to your vehicle would remain sealed and in perfect working order. You may already know that you should avoid exposing the all-important brake fluid to moisture or air, so you take steps to make sure that you always comply. However, this may not be enough by itself.

With time, tiny imperfections can appear throughout the system, where rubber seals may begin to perish or holes appear in hoses. In certain circumstances, this can allow air to penetrate into the braking system, especially as the brake pads wear down.

How Air Gets In

When your vehicle was fitted with new brake pads and fluid was originally installed, the system was indeed air tight and there was no room for any excess. However, as the friction material fitted to the brake pads begins to deteriorate, the pistons need to move closer to the brake discs; in turn, the brake fluid 'spreads out'. In these circumstances, air can then penetrate the system through one of those previously mentioned imperfections, and this can lead to additional problems.

Water Conversion

With air in the system, water may not be too far behind. Although brake fluid is designed to have a very high boiling point, it can nevertheless overheat with constant and heavy use. When the fluid itself boils, the air that is trapped within the system is converted into steam. Because brake fluid is hygroscopic, it will then absorb this steam and retain it as water.

Unfortunately, brake fluid is not designed to work well with water, and it will lose its consistency. When you try to slow the car down, you may notice that the pedal travels much further while you get that strange, spongy feeling underfoot. Unfortunately, it's just one of those things and has been caused by a combination of circumstances.

Taking Action

Nevertheless, you cannot drive your vehicle with an ineffective braking system. Therefore, your next course of action should be to get it fixed, so that you can take to the road again with full confidence.